/*
 * Source file for missing WinCE functionality
 * Copyright © 2012 RealVNC Ltd.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "missing.h"

#include <config.h>
#include <libusbi.h>

#include <windows.h>

// The registry path to store environment variables
#define ENVIRONMENT_REG_PATH _T("Software\\libusb\\environment")

/* Workaround getenv not being available on WinCE.
 * Instead look in HKLM\Software\libusb\environment */
char *getenv(const char *name)
{
    static char value[MAX_PATH];
    TCHAR wValue[MAX_PATH];
    WCHAR wName[MAX_PATH];
    DWORD dwType, dwData;
    HKEY hkey;
    LONG rc;

    if (!name)
        return NULL;

    if (MultiByteToWideChar(CP_UTF8, 0, name, -1, wName, MAX_PATH) <= 0) {
        usbi_dbg("Failed to convert environment variable name to wide string");
        return NULL;
    }
    wName[MAX_PATH - 1] = 0; // Be sure it's NUL terminated

    rc = RegOpenKeyEx(HKEY_LOCAL_MACHINE, ENVIRONMENT_REG_PATH, 0, KEY_QUERY_VALUE, &hkey);
    if (rc != ERROR_SUCCESS) {
        usbi_dbg("Failed to open registry key for getenv with error %d", rc);
        return NULL;
    }

    // Attempt to read the key
    dwData = sizeof(wValue);
    rc = RegQueryValueEx(hkey, wName, NULL, &dwType,
        (LPBYTE)&wValue, &dwData);
    RegCloseKey(hkey);
    if (rc != ERROR_SUCCESS) {
        usbi_dbg("Failed to read registry key value for getenv with error %d", rc);
        return NULL;
    }
    if (dwType != REG_SZ) {
        usbi_dbg("Registry value was of type %d instead of REG_SZ", dwType);
        return NULL;
    }

    // Success in reading the key, convert from WCHAR to char
    if (WideCharToMultiByte(CP_UTF8, 0,
            wValue, dwData / sizeof(*wValue),
            value, MAX_PATH,
            NULL, NULL) <= 0) {
        usbi_dbg("Failed to convert environment variable value to narrow string");
        return NULL;
    }
    value[MAX_PATH - 1] = 0; // Be sure it's NUL terminated
    return value;
}

